Generally, a shell fired by artillery or multiple rocket launcher on the ground is filled with high explosive powder inside its body, and has a penetrator disposed below in order to penetrate armored cars or tanks and is used in civilians killing or armored penetrating.
A fuse is installed at the top or bottom of the shell as means to ignite explosion of the high explosive powder. The fuse includes the kinds of a mechanical fuse which explodes by the impact force generated on the collision with targets or ground, a chemical delayed self-destruct fuse causing self-destruct after a while by firing powder in the mechanical fuse, and an electronic delayed self-destruct fuse causing self-destruct after a while by the timer installed in the fuse.
When the shells employing mechanical fuses reach up to predetermined height, the powder inside the shell is exploded, and the shells are spread to the air by the explosion pressure, and fall down on the ground.
However, it sometimes occurs that the electronic delayed self-destruct fuse including the mechanical fuse is unexploded when the shell employing such electronic delayed self-destruct fuse falls on snow, water, barriers on the ground, inclined-surface ground, and so on because it lacks impact force. The electronic delayed self-destruct fuse is structured to be self-destruct in the secondary way in the case that the mechanical fuse does not work primarily by the reason as above. When the shell falls down on the ground and bounces, it is sometimes hit to the ground or stones thereby causing the electronic delayed self-destruct fuse broken off. As a result, the secondary self-destruct function does not work and the shell is remained as unexploded. Such unexploded shells bring the problems to affect fatal damages on civilians or own armies by accidental explosion as well as harmful influence on the firepower of own armies.